vector.c

/*
 * $Id: vector.c,v 1.1.1.1 2003/03/16 07:03:49 kenta Exp $
 *
 * Copyright 2002 Kenta Cho. All rights reserved.
 */

/**
 * Vector functions.
 *
 * @version $Revision: 1.1.1.1 $
 */
#include <math.h>

#include "vector.h"

float
vctInnerProduct (Vector * v1, Vector * v2)
{
   return (float) v1->x * v2->x + (float) v1->y * v2->y;
}

Vector
vctGetElement (Vector * v1, Vector * v2)
{
   Vector ans;
   int ll = v2->x * v2->x + v2->y * v2->y;
   if (ll != 0) {
      int mag = vctInnerProduct (v1, v2);
      ans.x = mag * v2->x / ll;
      ans.y = mag * v2->y / ll;
   } else {
      ans.x = ans.y = 0;
   }
   return ans;
}

void
vctAdd (Vector * v1, Vector * v2)
{
   v1->x += v2->x;
   v1->y += v2->y;
}

void
vctSub (Vector * v1, Vector * v2)
{
   v1->x -= v2->x;
   v1->y -= v2->y;
}

void
vctMul (Vector * v1, int a)
{
   v1->x *= a;
   v1->y *= a;
}

void
vctDiv (Vector * v1, int a)
{
   v1->x /= a;
   v1->y /= a;
}

int
vctCheckSide (Vector * checkPos, Vector * pos1, Vector * pos2)
{
   int xo = pos2->x - pos1->x, yo = pos2->y - pos1->y;
   if (xo == 0) {
      if (yo == 0)
         return 0;
      return checkPos->x - pos1->x;
   } else if (yo == 0) {
      return pos1->y - checkPos->y;
   } else {
      if (xo * yo > 0) {
         return (checkPos->x - pos1->x) / xo - (checkPos->y - pos1->y) / yo;
      } else {
         return -(checkPos->x - pos1->x) / xo + (checkPos->y - pos1->y) / yo;
      }
   }
}

int
vctSize (Vector * v)
{
   return sqrt (v->x * v->x + v->y * v->y);
}

int
vctDist (Vector * v1, Vector * v2)
{
   int ax = absN (v1->x - v2->x), ay = absN (v1->y - v2->y);
   if (ax > ay) {
      return ax + (ay >> 1);
   } else {
      return ay + (ax >> 1);
   }
}